1. Field of the Invention
This invention relates to the electrochemical production of alkaline hydrogen peroxide solutions.
2. Description of the Prior Art
The production of alkaline hydrogen peroxide by the electroreduction of oxygen in an alkaline solution is well known from U.S. Pat. No. 3,607,687 to Grangaard and U.S. Pat. No. 3,969,201 to Oloman et al.
Improved processes for the production of an alkaline hydrogen peroxide solution by electroreduction of oxygen are disclosed in U.S. Pat. No. 4,431,494 to McIntyre et al. and in Canadian 1,214,747 to Oloman. These patents describe methods for the electrochemical generation of an alkaline hydrogen peroxide solution designed to decrease the hydrogen peroxide decomposition rate in an aqueous alkaline solution (McIntyre et al.) and to increase the current efficiency (Oloman). In McIntyre et al., a stabilizing agent is utilized in an aqueous electrolyte solution in order to minimize the amount of peroxide decomposed during electrolysis, thus, maximizing the electrical efficiency of the cell, i.e., more peroxide is recovered per unit of energy expended. In Oloman, the continually decreasing current efficiency of electrochemical cells for the generation of alkaline peroxide by the electroreduction of oxygen in an alkaline solution is overcome by the inclusion of a complexing agent in the aqueous alkaline electrolyte which is utilized at a pH of 13 or more. Both McIntyre et al. and Oloman utilize chelating agents as the stabilizing agent or complexing agents, respectively. Both McIntyre et al. and Oloman disclose the use of alkali metal salts of ethylene-diaminetetraacetic acid (EDTA) as useful stabilizing agents.
Electrochemical cells for the electroreduction of oxygen in an alkaline solution are disclosed in U.S. Pat. No. 4,872,957 and U.S. Pat. No. 4,921,587, both to Dong et al., and both incorporated herein by reference. In these patents, electrochemical cells are disclosed having a porous, self-draining, gas diffusion electrode and a microporous diaphragm. A dual purpose electrode assembly is disclosed in U.S. Pat. No. 4,921,587. The diaphragm can have a plurality of layers and may be a microporous polyolefin film or a composite thereof.
The present invention concerns a method for the electroreduction of oxygen in an alkaline solution in an electrochemical cell having a cell diaphragm or cell separator which is characterized as comprising a microporous film. Plugging of the pores of said film diaphragm during operation of the cell is avoided by the use of a stabilizing agent which can be a chelating agent.